// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
// Copyright (C) 2012 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

/* 
 
 * NOTE: This file is the modified version of xcolumn_bmod.c file in SuperLU 
 
 * -- SuperLU routine (version 3.0) --
 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
 * and Lawrence Berkeley National Lab.
 * October 15, 2003
 *
 * Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
 * EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program for any
 * purpose, provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is
 * granted, provided the above notices are retained, and a notice that
 * the code was modified is included with the above copyright notice.
 */
#ifndef SPARSELU_COLUMN_BMOD_H
#define SPARSELU_COLUMN_BMOD_H

namespace Eigen {

namespace internal {
    /**
 * \brief Performs numeric block updates (sup-col) in topological order
 * 
 * \param jcol current column to update
 * \param nseg Number of segments in the U part
 * \param dense Store the full representation of the column
 * \param tempv working array 
 * \param segrep segment representative ...
 * \param repfnz ??? First nonzero column in each row ???  ...
 * \param fpanelc First column in the current panel
 * \param glu Global LU data. 
 * \return 0 - successful return 
 *         > 0 - number of bytes allocated when run out of space
 * 
 */
    template <typename Scalar, typename StorageIndex>
    Index SparseLUImpl<Scalar, StorageIndex>::column_bmod(const Index jcol,
                                                          const Index nseg,
                                                          BlockScalarVector dense,
                                                          ScalarVector& tempv,
                                                          BlockIndexVector segrep,
                                                          BlockIndexVector repfnz,
                                                          Index fpanelc,
                                                          GlobalLU_t& glu)
    {
        Index jsupno, k, ksub, krep, ksupno;
        Index lptr, nrow, isub, irow, nextlu, new_next, ufirst;
        Index fsupc, nsupc, nsupr, luptr, kfnz, no_zeros;
        /* krep = representative of current k-th supernode
    * fsupc =  first supernodal column
    * nsupc = number of columns in a supernode
    * nsupr = number of rows in a supernode
    * luptr = location of supernodal LU-block in storage
    * kfnz = first nonz in the k-th supernodal segment
    * no_zeros = no lf leading zeros in a supernodal U-segment
    */

        jsupno = glu.supno(jcol);
        // For each nonzero supernode segment of U[*,j] in topological order
        k = nseg - 1;
        Index d_fsupc;  // distance between the first column of the current panel and the
                        // first column of the current snode
        Index fst_col;  // First column within small LU update
        Index segsize;
        for (ksub = 0; ksub < nseg; ksub++)
        {
            krep = segrep(k);
            k--;
            ksupno = glu.supno(krep);
            if (jsupno != ksupno)
            {
                // outside the rectangular supernode
                fsupc = glu.xsup(ksupno);
                fst_col = (std::max)(fsupc, fpanelc);

                // Distance from the current supernode to the current panel;
                // d_fsupc = 0 if fsupc > fpanelc
                d_fsupc = fst_col - fsupc;

                luptr = glu.xlusup(fst_col) + d_fsupc;
                lptr = glu.xlsub(fsupc) + d_fsupc;

                kfnz = repfnz(krep);
                kfnz = (std::max)(kfnz, fpanelc);

                segsize = krep - kfnz + 1;
                nsupc = krep - fst_col + 1;
                nsupr = glu.xlsub(fsupc + 1) - glu.xlsub(fsupc);
                nrow = nsupr - d_fsupc - nsupc;
                Index lda = glu.xlusup(fst_col + 1) - glu.xlusup(fst_col);

                // Perform a triangular solver and block update,
                // then scatter the result of sup-col update to dense
                no_zeros = kfnz - fst_col;
                if (segsize == 1)
                    LU_kernel_bmod<1>::run(segsize, dense, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
                else
                    LU_kernel_bmod<Dynamic>::run(segsize, dense, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
            }  // end if jsupno
        }      // end for each segment

        // Process the supernodal portion of  L\U[*,j]
        nextlu = glu.xlusup(jcol);
        fsupc = glu.xsup(jsupno);

        // copy the SPA dense into L\U[*,j]
        Index mem;
        new_next = nextlu + glu.xlsub(fsupc + 1) - glu.xlsub(fsupc);
        Index offset = internal::first_multiple<Index>(new_next, internal::packet_traits<Scalar>::size) - new_next;
        if (offset)
            new_next += offset;
        while (new_next > glu.nzlumax)
        {
            mem = memXpand<ScalarVector>(glu.lusup, glu.nzlumax, nextlu, LUSUP, glu.num_expansions);
            if (mem)
                return mem;
        }

        for (isub = glu.xlsub(fsupc); isub < glu.xlsub(fsupc + 1); isub++)
        {
            irow = glu.lsub(isub);
            glu.lusup(nextlu) = dense(irow);
            dense(irow) = Scalar(0.0);
            ++nextlu;
        }

        if (offset)
        {
            glu.lusup.segment(nextlu, offset).setZero();
            nextlu += offset;
        }
        glu.xlusup(jcol + 1) = StorageIndex(nextlu);  // close L\U(*,jcol);

        /* For more updates within the panel (also within the current supernode),
   * should start from the first column of the panel, or the first column
   * of the supernode, whichever is bigger. There are two cases:
   *  1) fsupc < fpanelc, then fst_col <-- fpanelc
   *  2) fsupc >= fpanelc, then fst_col <-- fsupc
   */
        fst_col = (std::max)(fsupc, fpanelc);

        if (fst_col < jcol)
        {
            // Distance between the current supernode and the current panel
            // d_fsupc = 0 if fsupc >= fpanelc
            d_fsupc = fst_col - fsupc;

            lptr = glu.xlsub(fsupc) + d_fsupc;
            luptr = glu.xlusup(fst_col) + d_fsupc;
            nsupr = glu.xlsub(fsupc + 1) - glu.xlsub(fsupc);  // leading dimension
            nsupc = jcol - fst_col;                           // excluding jcol
            nrow = nsupr - d_fsupc - nsupc;

            // points to the beginning of jcol in snode L\U(jsupno)
            ufirst = glu.xlusup(jcol) + d_fsupc;
            Index lda = glu.xlusup(jcol + 1) - glu.xlusup(jcol);
            MappedMatrixBlock A(&(glu.lusup.data()[luptr]), nsupc, nsupc, OuterStride<>(lda));
            VectorBlock<ScalarVector> u(glu.lusup, ufirst, nsupc);
            u = A.template triangularView<UnitLower>().solve(u);

            new (&A) MappedMatrixBlock(&(glu.lusup.data()[luptr + nsupc]), nrow, nsupc, OuterStride<>(lda));
            VectorBlock<ScalarVector> l(glu.lusup, ufirst + nsupc, nrow);
            l.noalias() -= A * u;

        }  // End if fst_col
        return 0;
    }

}  // end namespace internal
}  // end namespace Eigen

#endif  // SPARSELU_COLUMN_BMOD_H
